In an offshore oil well drilling vessel, it is necessary to rack drill pipe during drilling operations. The drill pipe may be in approximately 30 foot sections, the sections being joined by tool joints which are made and/or broken-out, as the case may be. When broken-out, the pipe may be stored in the racks generally in 90 foot lengths or three sections.
Various racking systems have been devised which are located in the hold of the drilling vessel and below the drilling platform. The lengths of drill pipe are handled by a hoist and are lowered into a pipe rack which may be a box to receive a number of the drill stands. Tubular racks are also known; at the bottom of each tube, there is a solid structure to support the drill pipe and tool joints. It is desirable to handle the drill strings rapidly and also in such fashion to avoid damage to threaded portions of the tool joints; thus in the absence of means to absorb shock when a drill string is lowered into its rack, damage to the string or tool joint can be expected. This reduces the life expectency of the drill string, increasing the cost of drilling.
It is possible to lower the drill string at a creep rate to avoid damage; this lengthens the total time for handling the string and thus adds to the cost of drilling.